O. Mauron

Observation of L-X-ray satellites and hypersatellites in collisions of O and Ne ions with Mo and Pd

Abstract The satellite structure of Lα 1,2 and Lβ 1 X-ray transitions in 42 Mo and 46 Pd induced by an impact of O and Ne ions with energies 178–376 MeV have been studied with a high-resolution von Hamos crystal spectrometer. The observed M-shell satellites of the diagram Lα 1,2 and Lβ 1 lines are affected mostly by one- and two-vacancy configurations for oxygen ions and much more complex multi-vacancy configurations for neon impact. The L-shell hypersatellites are clearly observed in the measured spectra, both for Lα 1,2 and Lβ 1 X-ray transitions. The spectra are compared with the predictions of the multi-configuration Dirac–Fock (MCDF) calculations performed for up to two additional vacancies. Such MCDF calculations reproduce the main features of the M-shell satellite structure observed for oxygen ions, but they fail to describe the X-ray spectra measured for neon ions. Clearly, more complex multi-vacancy configurations have to be included in the MCDF calculations to achieve quantitative agreement in this case. The measured X-ray satellite structure for neon ions is thus interpreted by means of a simplified binomial model based on the average MCDF X-ray shifts and independent electron picture of multiple ionization of atoms by ion impact.

Observation of internal structure of the L-shell x-ray hypersatellites for palladium atoms multiply ionized by fast oxygen ions

An observation of the internal structure of the L-shell hypersatellite x rays resulting from the one-photon decay of L{sup -2} double-vacancy states in palladium multiply ionized by oxygen ions is reported. The Pd L{sub 3}{yields}M{sub 4,5} x-ray spectrum was measured with a von Hamos high-resolution crystal spectrometer. The complex shape of the observed spectrum could be interpreted in detail using relativistic multiconfiguration Dirac-Fock calculations. The relative intensities of the measured x rays were found to be in good agreement with semiclassical approximation calculations using relativistic Dirac-Hartree-Fock wave functions.

Vacancy rearrangement processes in multiply ionized atoms

We demonstrate that in order to interpret the x-ray satellite structure of Pd Lα1,2(L3M4,5) transitions excited by fast O ions, which was measured using a high-resolution von Hamos crystal spectrometer, the vacancy rearrangement processes, taking place prior to the x-ray emission, have to be taken into account. The measured spectra were compared with the predictions of the multi-con.guration Dirac-Fock (MCDF) calculations using the fluorescence and Coster-Kronig yields which were modiffed due to a reduced number of electrons available for relaxation processes and the effect of closing the Coster-Kronig transitions. We demonstrate that the vacancy rearrangement processes can be described in terms of the rearrangement factor, which can be calculated by solving the system of rate equations modelling the flow of vacancies in the multiply ionized atom. By using this factor, the ionization probability at the moment of collision can be extracted from the measured intensity distribution of x-ray satellites. The present results support the independent electron picture of multiple ionization and indicate the importance of use of Dirac-Hartree-Fock wave functions to calculate the ionization probabilities.

M-subshell ionization in near-central collisions of 20-MeV/amu carbon ions with molybdenum atoms

Abstract The Kβ spectrum of 42 Mo bombarded by 20.8 MeV/amu carbon ions was measured with high-resolution using a transmission-type bent crystal spectrometer operated in the modified DuMond slit geometry. The M-shell satellites of the Kβ 2 transition could be well resolved, whereas for the Kβ 1,3 transitions only a broadening and shift of the line centroid was observed. The composite structure of the satellite lines which consist of many components that vary in energy and strength was analyzed using theoretical energies and relative intensities obtained from multiconfiguration Dirac–Fock calculations. From the data analysis average M-shell satellite-to-diagram line yield ratios were deduced for both the Kβ 1,3 and Kβ 2 transitions. For the Kβ 2 transition for which the relative contributions of the 3s,p and 3d spectator vacancies to the observed Kβ 2 M 1 satellite yield could be determined, separated X(Kβ 2 M 1 1,2,3 ):X(Kβ 2 M 0 ) and X(Kβ 2 M 1 4,5 ):X(Kβ 2 M 0 ) yield ratios could even be extracted.

High energy resolution measurements of the radiative decay of double K-shell vacancies in 20 ≤ Z ≤ 29 elements bombarded by fast C and Ne ions

We report on high energy resolution measurements of the Kα hypersatellite x-ray spectra of Ca, V, Fe and Cu induced by impact with 144 MeV C and 180 MeV Ne ions.

The satellites and hypersatellites of Lα1 2 and Lβ1 x-ray transitions in zirconium excited by oxygen and neon ions

The interpretation of L-shell satellites and hypersatellites for Lα1,2 (L3→M4,5) and Lβ1 (L2→M4) x-ray transitions in zirconium multiply ionized by oxygen and neon ions is reported. The x-ray spectra were measured with a high-resolution von Hamos spectrometer and interpreted in terms the relativistic multi-configuration Dirac-Fock (MCDF) calculations. The ionization probabilities of L- and M-shell derived from the data are compared with the predictions of the semiclassical approximation (SCA) calculations.